packaging(rpm): Fedora 44 build + ship the KDE session unit & host.env

Three changes to make a reproducible Fedora KDE host install:
- ci/fedora-rpm.Dockerfile: parameterize the Fedora base (ARG FEDORA_VERSION, default 43) so the
  same builder produces the Bazzite (F43, libavcodec.so.61) and Fedora 44 (libavcodec.so.62) RPMs.
  A binary RPM is soname-coupled to its base, so each target Fedora needs its own build/channel.
- spec: install punktfunk-kde-session.service (was in the tree but never packaged) with its
  ExecStart repointed from the dev source tree to the installed run-headless-kde.sh. This is the
  headless `kwin --virtual` session (KWIN_WAYLAND_NO_PERMISSION_CHECKS=1) the kwin backend needs —
  an interactive Plasma session refuses to hand its privileged zkde_screencast protocol to an
  external client, so a dedicated session is required. Not enabled by default (kwin hosts opt in).
- ship packaging/kde/host.env as host.env.kde — the ready KWin appliance config (wayland-kde).

Validated live on a Fedora 44 KDE box (RTX 4090): KWin virtual output + zero-copy dmabuf->CUDA->NVENC.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ci/fedora-rpm.Dockerfile

@@ -1,11 +1,15 @@
-# CI builder for the punktfunk RPM — Fedora 43 to match Bazzite's base (so the RPM's
-# auto-generated library Requires, e.g. libavcodec.so.NN, pin to exactly what the target
-# runs). Used by .gitea/workflows/rpm.yml; built+pushed by .gitea/workflows/docker.yml.
+# CI builder for the punktfunk RPM. The Fedora version is parameterized so one Dockerfile
+# serves every target whose ffmpeg soname must match: Fedora 43 == Bazzite's base (group
+# "bazzite"), Fedora 44 == the Fedora KDE spin (group "fedora-44"). The RPM's auto-generated
+# library Requires (e.g. libavcodec.so.NN) pin to exactly what the chosen base — and thus the
+# target — ships. Used by .gitea/workflows/rpm.yml; built+pushed by .gitea/workflows/docker.yml.
 #
-#   docker build -f ci/fedora-rpm.Dockerfile -t punktfunk-fedora-rpm ci
+#   docker build --build-arg FEDORA_VERSION=43 -f ci/fedora-rpm.Dockerfile -t punktfunk-fedora-rpm ci
+#   docker build --build-arg FEDORA_VERSION=44 -f ci/fedora-rpm.Dockerfile -t punktfunk-fedora44-rpm ci
 #
 # Mirrors ci/rust-ci.Dockerfile (the Ubuntu workspace builder) for the rpmbuild side.
-FROM fedora:43
+ARG FEDORA_VERSION=43
+FROM fedora:${FEDORA_VERSION}
 
 # RPM Fusion (free + nonfree) provides the NVENC-capable ffmpeg-devel the host links against.
 RUN dnf -y install \